1. Field of the Invention
This invention relates to an ultrasonic motor utilizing an ultrasonic vibration.
2. Description of the Related Art
One type of conventionally known ultrasonic motor is disclosed in Japanese laid-open Patent Application No.2-290171, for example. The amplitude of vibration induced in an elastic member is small in conventional ultrasonic motors, and in view of this point, the above Laid-open Patent Application describes the necessity of an extremely-highly accurate processing for a surface of the elastic member at the contact side thereof with a rotor using a surface polishing working technique to improve flatness of the surface of the elastic member.
However, the conventional ultrasonic motor as described above adopts such a surface polishing working technique that the whole area of the surface of the elastic member at the contact side with the rotor is polished. It takes a long time to perform the surface polishing, working and the manufacturing cost is increased.